<s>
The	O
Olympus	B-Algorithm
OM	I-Algorithm
System	I-Algorithm
was	O
a	O
line	O
of	O
35mm	O
single-lens	B-Algorithm
reflex	I-Algorithm
cameras	I-Algorithm
,	O
lenses	O
and	O
accessories	O
sold	O
by	O
Olympus	O
between	O
1972	O
and	O
2002	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
the	O
M	O
system	O
was	O
renamed	O
OM	B-Algorithm
System	I-Algorithm
.	O
</s>
<s>
All	O
the	O
consumer-grade	O
models	O
were	O
discontinued	O
after	O
1992	O
,	O
since	O
the	O
market	O
for	O
manual-focus	O
SLR	B-Algorithm
cameras	I-Algorithm
had	O
declined	O
greatly	O
in	O
favour	O
of	O
autofocus	O
SLRs	B-Algorithm
.	O
</s>
<s>
The	O
Olympus	O
OM-1	O
was	O
a	O
manually-operated	O
35mm	O
single-lens	B-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
forming	O
the	O
basis	O
of	O
the	O
OM	B-Algorithm
system	I-Algorithm
in	O
1972	O
.	O
</s>
<s>
One	O
feature	O
unique	O
to	O
the	O
OM-1	O
,	O
compared	O
to	O
the	O
rest	O
of	O
the	O
OM	B-Algorithm
system	I-Algorithm
,	O
was	O
its	O
mirror	O
lock-up	O
facility	O
which	O
made	O
it	O
ideal	O
for	O
astrophotography	O
and	O
macrophotography	O
.	O
</s>
<s>
Introduced	O
in	O
1975	O
,	O
the	O
Olympus	O
OM-2	O
was	O
a	O
semi-automatic	O
,	O
aperture-priority	B-Algorithm
camera	O
featuring	O
an	O
electronically	O
controlled	O
shutter	O
.	O
</s>
<s>
It	O
also	O
featured	O
an	O
LCD	B-Device
similar	O
to	O
the	O
OM-4	O
which	O
could	O
be	O
illuminated	O
in	O
low	O
light	O
.	O
</s>
<s>
Batteries	O
were	O
only	O
needed	O
for	O
the	O
exposure	O
meter	O
and	O
LCD	B-Device
.	O
</s>
<s>
It	O
was	O
a	O
battery-powered	O
,	O
electromechanically	O
controlled	O
,	O
manual	O
focus	O
SLR	B-Algorithm
with	O
manual	O
exposure	O
control	O
or	O
aperture	B-Algorithm
priority	I-Algorithm
autoexposure	O
.	O
</s>
<s>
It	O
used	O
a	O
graduated	O
linear	O
LCD	B-Device
for	O
the	O
shutter	O
speed	O
at	O
the	O
bottom	O
of	O
the	O
viewfinder	O
to	O
precisely	O
indicate	O
its	O
readings	O
versus	O
the	O
actual	O
camera	O
settings	O
.	O
</s>
<s>
The	O
camera	O
was	O
a	O
35mm	O
focal-plane	O
shutter	O
aperture	B-Algorithm
priority	I-Algorithm
AE	O
SLR	B-Algorithm
camera	I-Algorithm
with	O
an	O
electronic	O
shutter	O
.	O
</s>
<s>
Only	O
aperture-priority	B-Algorithm
AE	O
was	O
available	O
with	O
the	O
camera	O
unless	O
the	O
optional	O
manual	O
exposure	O
adapter	O
was	O
installed	O
.	O
</s>
<s>
Exposure	O
control	O
was	O
aperture	B-Algorithm
priority	I-Algorithm
AE	O
using	O
center-weighted	B-Algorithm
light	I-Algorithm
metering	I-Algorithm
.	O
</s>
<s>
The	O
OM-20	O
also	O
had	O
a	O
built-in	O
shutter-speed	O
dial	O
,	O
a	B-Algorithm
mode	I-Algorithm
display	O
in	O
the	O
view	O
finder	O
and	O
a	O
much	O
stronger	O
winding	O
mechanism	O
which	O
permitted	O
it	O
to	O
be	O
used	O
at	O
5	O
frames	O
per	O
second	O
on	O
the	O
OM	O
Motor	O
Drive	O
2	O
.	O
</s>
<s>
It	O
also	O
had	O
an	O
early	O
form	O
of	O
matrix	B-Algorithm
metering	I-Algorithm
,	O
and	O
a	O
mirror	O
lock-up	O
facility	O
.	O
</s>
<s>
OM	O
lenses	O
also	O
featured	O
a	O
depth-of-field	O
preview	O
button	O
on	O
the	O
lens	O
,	O
in	O
contrast	O
to	O
most	O
other	O
SLR	B-Algorithm
camera	I-Algorithm
systems	O
,	O
in	O
which	O
the	O
button	O
was	O
placed	O
on	O
the	O
camera	O
body	O
.	O
</s>
